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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image processing apparatus, such as an image
processing apparatus having a function for detecting a specific image,
such as that of a bank note or security.
2. Description of the Prior Art
Apparatus of this type that have recently been developed feature a large
number of tones and a high-image quality in which an image signal
expressing one pixel is composed of a large number of bits. Owing to
greater sophistication of image processing and an improvement in recording
density, even a binary printer is capable of providing a high picture
quality approaching that of a multivalued printer.
However, the recent improvements in the picture quality of copying machines
which now have a color capability have been accompanied by the fear of
counterfeiting, in which specific originals such as bank notes and
securities, which are not meant to be copied, are duplicated at such a
high picture quality that the copies are almost indistinguishable from the
originals.
Thus, a serious shortcoming in the prior art mentioned above is that
effective measures for preventing counterfeiting have not been developed
for binary printers in which one pixel is expressed by one bit (in the
case of color, by the three bits, namely R, G, B bits, or by four bits,
namely C, M, Y and Bk bits).
SUMMARY OF THE INVENTION
An object of the invention is to provide an image processing apparatus
capable of eliminating the aforementioned drawback of the prior art.
Another object of the invention is to provide an image processing apparatus
in which, when an original attempting to be copied is identical with a
specific image, output can be controlled not only in case of multivalued
image data but also when binary image data is outputted.
Still another object of the invention is to provide an image processing
apparatus in which, when an original attempting to be copied is identical
with a specific image, output can be controlled by an inexpensive hardware
configuration non only in case of multivalued image data but also when
binary image data is outputted.
A further object of the invention is to provide an image processing
apparatus in which, even if the invention is applied to a binary printer,
it is possible to perform processing to determine whether a specific color
original is present, in accordance with image data, in order to prevent
copying of the specific original or recording of specific-image data
inputted from an external device such as a computer.
Yet another object of the invention is to provide an image processing
apparatus comprising generating means for generating color data based upon
inputted binary image data, judging means for judging identity between the
color data generated by the generating means and color data of a plurality
of different specific images, and control means for controlling output of
the inputted binary image data based upon results of judgment made by the
judging means.
Yet another object of the invention is to provide an image processing
apparatus comprising conversion processing means for converting inputted
multivalued image data into binary image data, generating means for
generating color data based upon the binary image data resulting from the
conversion performed by the conversion processing means, judging means for
judging identity between the color data generated by the generating means
and color data of a plurality of different specific images, and control
means for controlling output of the binary image data, which results from
the conversion performed by the conversion processing means, based upon
results of judgment made by the judging means.
Other features and advantages of the present invention will be apparent
from the following description taken in conjunction with the accompanying
drawings, in which like reference characters designate the same or similar
parts throughout the figures thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an external perspective view showing the configuration of a
digital color copier according to a first embodiment of the present
invention;
FIG. 2 is a sectional side view showing the internal construction of the
digital color copier of FIG. 1;
FIG. 3 is a diagram showing a scanning carriage and parts peripheral
thereto according to the first embodiment;
FIG. 4 is a diagram showing the mechanism within a scanner according to the
first embodiment;
FIG. 5 is a diagram for describing a reading operation at the time of a
book mode and sheet mode according to the first embodiment;
FIG. 6 is a block diagram showing the construction of a digital color
copier according to the first embodiment;
FIG. 7 is a timing chart of an image between circuit blocks described in
FIG. 6;
FIG. 8 is a block diagram showing the construction of an image judging unit
according to the first embodiment;
FIG. 9 is a diagram for describing the processing performed by a
binary/multivalue converter according to the first embodiment;
FIG. 10 is a diagram for describing the processing performed by a
binary/multivalue converter according to the first embodiment;
FIG. 11 is a diagram for describing the processing performed by a
binary/multivalue converter according to the first embodiment;
FIG. 12 is a diagram for describing a method of thinning out image data and
subjecting the image data to a multivalued conversion according to the
first embodiment;
FIG. 13 is a block diagram illustrating the construction of an integrator
according to the first embodiment;
FIG. 14 is a diagram showing an example of the input/output of the
integrator according to the first embodiment;
FIG. 15 is a diagram showing an example of the input/output of the
integrator according to the first embodiment;
FIG. 16 is a diagram showing an example of processed results according to
the first embodiment;
FIG. 17 is a block diagram illustrating the construction of an image
judging unit according to a second embodiment of the invention;
FIG. 18 is a block diagram showing the construction of a principal portion
of an image judging unit according to a third embodiment of the invention;
and
FIG. 19 is a timing chart of signals in the image judging unit shown in
FIG. 18.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiment of the present invention will now be described in
detail with reference to the accompanying drawings.
Though the present invention is applied to a copier in the embodiments to
follow, it goes without saying that the invention is applicable to other
types of apparatus as well. In addition, in each apparatus applicable to
the invention, specific originals such as bank notes, securities and
confidential documents are to be prevented from being counterfeited.
<First Embodiment>
FIG. 1 is an external perspective view showing the configuration of a
digital color copier according to a first embodiment of the present
invention.
The upper part of the apparatus shown in FIG. 1 comprises a color image
scanning section 1 (hereinafter referred to as a "scanning section") for
outputting digital color image data, and a controlling unit 2 accommodated
within the scanning section 1 for subjecting the digital color image data
to various types of image processing and having a processing function such
as that for interfacing an external device.
The lower part of the apparatus in FIG. 1 is a printing section 3 for
recording on recording paper the color digital image signal outputted by
the controlling unit 2.
The two sections mentioned above are capable of being separated and can be
installed at separate locations by lengthening the connecting cable.
FIG. 2 is a sectional side view showing the internal construction of the
digital color copier illustrated in FIG. 1.
The image of an original placed upon a glass platen 17, an image projected
by a projector, or the image of a sheet original from an output feed
mechanism 12 is read by an exposure lamp 14, a lens 15 and a CCD line
sensor 16 using a CCD that is capable of reading a line image in full
color. Various types of image processing are executed by the scanning
section 1 and controlling unit 2 to record the image on recording paper by
the printing section 3.
In FIG. 2, the recording paper is supplied from a paper-feed cassette 20,
which accommodates paper cut to a small size (sizes A4 to A3 in this
embodiment), and a paper roll 29 used for recording in large size (sizes
A2 to A1 in this embodiment).
By introducing recording paper one sheet at a time from a manual-insertion
opening 22 (FIG. 1) while guiding it along a paper-feed cover 21, the
recording paper can be introduced manually from outside the apparatus.
This is referred to as "manual feed". A pick-up roller 24 is for feeding
the paper from the paper-feed cassette 20 one sheet at a time. The cut
sheets thus supplied are conveyed to a first paper-feed roller 26 by
cut-paper feed rollers 25. The rolled paper 29 is fed out by a
rolled-paper feed roller 30 and is cut to a fixed length by a cutter 31.
The paper thus cut is conveyed to the first paper-feed roller 26.
Similarly, recording paper inserted from the manual insertion opening 22
is conveyed to the first paper-feed roller 26 by manual-insertion rollers
32.
The pick-up roller 24, cut-paper feed rollers 25, rolled-paper feed roller
30, first paper-feed roller 26 and manual-insertion rollers 32 are driven
by a paperfeed motor (such as a DC servomotor), not shown, and can be
started and stopped whenever necessary by electromagnetic clutches
attached thereto.
When a printing operation starts in response to a command from the
controlling unit 2, the recording paper selectively fed by any of the
aforementioned paper-feed paths is conveyed to the first paper-feed roller
26. In order to prevent the recording paper from being fed while askew,
the first paper-feed roller 2 is turned on to convey the recording paper
to a second paper-feed roller 27 after a paper loop of a prescribed
quantity of paper is formed.
A buffer is formed between the first paper-feed roller 26 and the second
paper-feed roller 27 to provide the recording paper with a prescribed
amount of slack in order to assure that an accurate feeding operation will
take place between a paper-feed roller 28 and the second paper-feed roller
27. A sensor 33 senses the amount of buffer. By forming the buffer at all
times during conveyance of the paper, it is possible to reduce the load
upon the paper-feed roller 28 and second paper-feed roller 27 and assure
accurate paper feed in a case where large-sized recording paper is
conveyed.
When printing is performed by a recording head 37, a scanning carriage 34
on which the recording head 37 is mounted is made to scan back and forth
on carriage rails 36 by means of a scanning motor 35. Only a prescribed
amount of the recording paper is fed by the paper-feed roller 28 as the
recording head 57 is made to scan one way. At this time the
above-mentioned drive system is controlled in such a manner that a
prescribed buffer quantity is formed at all times by the paper-feed motor
while sensing is performed by the buffer sensor 33.
The recording paper on which printing has been performed is ejected into a
paper tray 23 to complete the printing operation.
FIG. 3 is a diagram illustrating the scanning carriage 34 and parts
peripheral thereto according to the first embodiment.
As shown in FIG. 3, a paper-feed motor 40 serves as a drive source for
intermittently feeding the recording paper. The motor 40 drives the
paper-feed roller 28 and the second paper-feed roller 27, the latter via a
second paper-feed roller clutch 43. The scanning motor 35 is a drive
source which causes the scanning carriage 34 to perform scanning in the
directions of arrows A and B via a scanning belt 34. In this embodiment,
pulse motors are used for the paper-feed motor 40 and scanning motor 35 if
highly accurate control of paper feed is required. When the recording
paper arrives at the second paper-feed roller 27, the second paper-feed
roller clutch 43 and the paper-drive motor 40 are turned on to convey the
recording paper to the paper-feed roller 28 along a platen 39.
The recording paper is sensed by a paper sensor 44 provided on the platen
39. The sensor information is utilized in positional control and to
control jamming.
When the recording paper reaches the paper-feed roller 28, the second
paper-feed roller clutch 43 and paper-feed motor 40 are turned off, a
suction operation is performed by a suction motor (not shown) from the
inner side of the platen 39 so that the recording paper will attracted to
the platen 39.
Before the recording paper is subjected to an image-recording operation,
the scanning carriage 34 is moved to the position of a home-position
sensor 41 and is then made to scan one way, namely in the direction of
arrow A. An image is recorded on the recording paper by jetting inks of
the colors cyan (C), magenta (M), yellow (Y) and black (K) from the
recording head 37 at a prescribed position. When the recording of an image
of a predetermined length ends, the scanning carriage 34 is halted and
scanning in the return direction, namely the direction of arrow B, begins.
As a result, the scanning carriage 34 returns to the position of the
home-position sensor 41. During this two-way scan, the recording paper is
fed in the direction of arrow C by the length of recording performed
thereon by the recording head 37. This feeding of the recording paper is
carried out by driving the paper-feed roller 28 using the paper-feed motor
40.
In this embodiment, the recording head 37 is an ink-jet nozzle of the kind
described above; 256 nozzles are assembled for each of the colors Y, M, C
and K, for a total of four recording-head assemblies.
When the scanning carriage 34 stops at the home position sensed by the
home-position sensor 41, an operation for recovering the recording head 37
is performed. This is processing for carrying out a stable recording
operation. In order to prevent an irregularity in the ink-jetting start
time as caused by a variation in the viscosity of the ink remaining in the
nozzles of the recording head 37, processing to apply pressure to the
recording head 37 or to discharge the ink with air is carried out
depending upon conditions programmed in advance, such as paper-feed time,
temperature within the apparatus and jetting time, etc.
Image recording over the entire surface of the recording paper is carried
out by repeating the operation described above.
The operation of the scanning section 1 will now be described.
FIG. 4 is a diagram showing the mechanism within the scanning section 1
according to the first embodiment.
A CCD unit 18 is composed of the CCD line sensor 16 and the lens 15, etc.
The CCD unit 18 is driven on rail 54 by a drive system, for the main
scanning direction, comprising a main-scanning motor 50, a pulley 51, a
pulley 52 and a wire 53 secured to the rail 54, whereby the image of the
original on the glass platen 17 is read in the main scanning direction. A
light-shield 55 and a home-position sensor 56 are used for positional
control when the CCD unit 18 is moved to the home position on the main
scan. The home position is located in a correction area 68.
The rail 54 is placed upon rails 65, 69 and is moved by a drive system,
which is for the subordinate scanning direction, comprising a
subordinate-direction scanning motor 60, pulleys 67, 68, 71, 76, shafts
72, 73 and wires 66, 70. A light shield 57 and home-position sensors 58,
59 are used for positional control when the rail 54 is moved to respective
subordinate-scanning home positions in the book mode, which is for reading
a book or the like placed upon the glass platen 17.
A sheet feeding motor 61, sheet feeding rollers 74, 75, pulleys 62, 64 and
a wire 63 constitute a mechanism for feeding an original in the form of a
sheet. This mechanism is for feeding, in prescribed incremental amounts by
means of the sheet feeding rollers 74, 75, a sheet original placed
face-down on the glass platen 17.
FIG. 5 is a diagram for describing a reading operation at the time of a
book mode and sheet mode according to the first embodiment.
In the book mode, the CCD unit 18 is moved to the book-mode home position
(indicated by "Book Mode HP" in FIG. 5), which is located in the
correction area 68. From this position, the CCD unit 18 starts to read the
entire surface of the original placed upon the glass platen 17.
Before the original is scanned, parameters necessary for such processing as
a shading correction, black-level correction and color correction are set
within the correction area 68. Thereafter, scanning in the main scanning
direction is started by the mainscanning motor 50 in the direction
indicated by the arrows. When reading of the area indicated by 1 ends, the
main-scanning motor 50 is reversed and the subordinate-scanning motor 60
in driven in the subordinate-scanning direction to effect movement to the
correction area 68 of area 2. Next, if necessary, processing such as the
shading correction, black-level correction and color correction is
performed in the same manner as in the main scanning of area 1, and then
the reading of area 2 is performed.
By repeating the scanning described above, the entire surface of areas 1
through 7 is read. After the reading of area 7 ends, the CCD unit 18 is
again returned to the book-mode home position.
In this embodiment, the glass platen 17 must actually be scanned a greater
number of times in order for an original of maximum size A2 to be read.
However, this procedure is omitted from the discussion in order to
facilitate an understanding of operation.
In the sheet mode, the CCD unit 18 is moved to the sheet-mode home position
("Sheet Mode HP" in FIG. 5) to repeatedly read area 8 of the sheet
original while the sheet feeding motor 61 is operated intermittently,
thereby reading the entire surface of the sheet original.
Before the original is scanned, processing such as a shading correction,
black-level correction and color correction is executed within the
correction area 68, after which scanning in the main scanning direction is
started by the main-scanning motor 50 in the direction indicated by the
arrows. When one-way reading of the area 8 ends, the main-scanning motor
50 is reversed and the sheet feeding motor 61 in driven to move the sheet
original a predetermined amount in the subordinate-scanning direction. A
similar operation is then repeated to read the entire surface of the sheet
original.
If the reading operation described above is performed at a magnification of
1X, the area read by the CCD unit 18 actually is a larger area, as
illustrated in FIG. 5. The reason for this is that the digital color
copier of this embodiment incorporates a zoom function for enlargement or
reduction. More specifically, the area capable of being recorded on by the
recording head 37 is fixed at 256 bits for one recording operation, as
mentioned above. Therefore, in a case where a 50% reduction is to be
performed, for example, image information of an area of at least 512 bits,
which is twice the number of bits, is required. Accordingly, the scanning
section 1 incorporates a function for reading and outputting the image
information of any image area by a single main-scanning reading operation.
FIG. 6 is a block diagram showing the construction of a digital color
copier according to the first embodiment. Controllers 102, 111, 121 are
control circuits for controlling the scanning section 1, controlling unit
2 and printing section 3. Each controller is constituted bV a
microcomputer, a program ROM, a data memory and a communication circuit,
etc. The controller 102 is connected to the controller 111 by a
communication line, and the controller 111 is connected to the controller
121 by a communication line. In response to a command from the controller
111, the controllers 102, 121 operate. In other words, a so-called
mast-slave control configuration is adopted.
In a case where the apparatus operates as a color copier, the controller
111 operates in accordance with an input command from a control panel 10
and from a digitizer 114.
The control panel 10 employs a liquid crystal (LCD display 84) as a display
unit, and the front side thereof is equipped with a touch panel 85
comprising transparent electrodes so that designation of color,
designation of an editing operation, etc., may be selectively performed.
In addition, the control panel 10 is provided with independent keys having
a high frequency of use, such as keys relating to operation. For example,
these keys include a start key 87 for designating the start of the copying
operation, a stop key 88 for designating stopping of the copying
operation, a reset key 89 for restoring the operation mode to a standard
state, and a projector key 86 for selecting a projector, which are not
shown.
Furthermore, the control panel 10 is provided with a mode selection key for
selecting one of a first and second mode, the first mode for processing
image data read by the CCD line sensor 16, and the second mode for
processing image data inputted by the I/F controller 112.
The digitizer 114 is for inputting position information indicating an area
to undergo trimming processing, masking processing or color-conversion
processing. The digitizer 114 is connected as an option if complicated
editing processing is required.
The controller 111 is for controlling the I/F controller 112, which is a
universal parallel interface such as an IEEE-488, namely a so-called GP-IB
interface. The controller 111 is adapted in such a manner that
input/output of image data with an external device as well as mode control
by an external device can be performed via this interface.
Furthermore, the controller 111 controls a multivalued synthesizer 106, an
image processor 107, a binarizing processor 108, a binary synthesizer 109
and a buffer memory 110, which are for subjecting an image to a variety of
processing.
The controller 102 controls a mechanical drive unit 105 which drives and
controls the mechanism of the scanning section 1 described above, an
exposure control unit 103 which controls exposure of a lamp for reflective
reading of an original, and an exposure control unit 104 which controls
exposure of a halogen lamp 90 when a projector is used. The controller 102
controls also an analog-signal processor 10 and an input-image processor
101, which subject an image to various processing.
The controller 121 controls the mechanical drive 105 which drives and
controls the mechanism of the printing section 3 described above, and a
synchronous delay memory 115 for absorbing disparities in time in the
mechanical operation of the printing section 3 and for correcting a delay
due to the arrangement of the mechanisms of recording heads 117 through
120.
The image processing blocks of FIG. 6 will now be described in connection
with the flow of image processing.
The image formed on the CCD line sensor 16 is converted into an analog
electric signal by the CCD 16. The image information resulting from the
conversion is serially processed in the manner
red.fwdarw.green.fwdarw.blue for each pixel and the processed results are
inputted to the analog-signal processor 100 . The analog-signal processor
100 subjects the information to an analog-to-digital conversion after
performing sampling and holding, dark-level correct ion and dynamic-range
control for each of the colors red, green and blue. The information is
thus converted into a serial multivalued digital image signal (in this
embodiment, a bit length of eight bits for each color), and the image
signal is outputted to the input-image processor 101.
In the input-image processor 101, the correction processing necessary in
the reading system, such as a shading correction, color correction and
.gamma.-correction, is performed, with the signal remaining in the form of
a serial multivalued digital image signal.
The multivalued synthesizer 106 in the controlling section 2 selects one of
the serial multivalued digital image signal sent from the scanning section
1 and the serial multivalued digital image signal sent via the parallel
I/F from the expanded device (a still video camera, a host computer,
etc.), or performs synthesizing processing both of them. The selected
image data is sent to the image processor 107 or the buffer memory 110 in
the form of a serial multivalued digital image signal. The synthesizing
processing includes one synthesis by multiplication of both of the serial
multivalue of digital image signals and another synthesis by giving prior
to one of the multivalued digital image signals.
The image processor 107 is a circuit for performing smoothing processing,
edge emphasis, black extraction and masking processing, which is for a
color correction of the recording ink used in the recording heads 117-120.
Each of the serial multivalued digital image signals Y, M, C and K
outputted by the image processor 107 is inputted to the binarizing
processor 108 or the buffer memory 110. The binarizing processor 108 is a
circuit for binarizing the serial multivalued digital image signals Y, M,
C and K respectively and is capable of selecting pure binary values based
upon a fixed slice level or pseudo-half-tone processing based upon the
dither method. Here the serial multivalued digital image signals Y, M, C
and K are converted into binary parallel image signal of four colors Y, M,
C and K. Four-color image data (Y, M, C and K) is sent to the binary
synthesizer 109, or the buffer memory 110. The binary synthesizer 109
selects one of the binary parallel image signal of four colors Y, M, C and
K sent from the buffer memory 110 and the binary parallel image signal of
four colors Y, M , C and K sent from the binary processor 108, or combines
both of the signals and forms a binary parallel image signal of four
colors Y, M, C and K. The buffer memory 110, which is for performing
input/output of a multivalued image and binary image via the parallel I/F,
and possesses memories for four colors.
According to the present embodiment, the below data input/output can be
made possible via the I/F controller 112 between the digital color copier
and an external device (a host computer etc. ) . Namely, a kind of data
includes multivalued image signals R, G and B 1, multivalued image signals
Y, M, C and K 2, and binary image signals Y, M, C and K 3. Data from the
external device is stored in the buffer memory 110, and inputted in the
multivalued synthesizer 106 or the image processor 107(a) , the binarizing
processor 108(b), and the binary synthesizer 109(c). In the similar
manner, each data of 1, 2 and 3 is stored in the buffer memory 110, and
outputted to the external device.
The synchronous delay memory 115 of the printing section 3 is a circuit for
absorbing disparities in time in the mechanical operation of the printing
section 3 and for correcting a delay due to the arrangement of the
mechanisms of recording heads 117 through 120. In addition, the memory 115
internally generates the timing necessary for driving the recording heads
117 through 120. A head driver 116 is an analog drive circuit which drives
the recording heads 117 through 120. The head driver 116 internally
generates signals that are capable of directly driving the recording heads
117 through 120. The recording heads 117 through 120 jet the inks of the
colors cyan, magenta, yellow and black to record an image on the recording
paper.
FIG. 7 is a timing chart of an image between the circuit blocks described
in FIG. 6.
A signal BVE indicates the effective interval of the image every scan of
the main-scan reading operation described in connection with FIG. 5. A
full frame of the image is outputted by outputting the signal BVE a
plurality of times.
A signal VE indicates the effective interval of the image every line read
by the CCD line sensor 16. The signal VE is rendered effective only when
the signal BVE is effective.
A signal VCD is a clock signal for forwarding image data VD. Both the
signal BVE and the signal VE vary in synch with the signal VCK.
A signal HS in used in a case where the signal VE repeatedly exhibits
effective and ineffective intervals discontinuously while one line is
being outputted. The signal HS is unnecessary in a case where the signal
VE is effective continuously while one line is being outputted. The signal
HS is a signal indicating the start of image output of one line.
Numeral 123 denotes an image judging unit. The binary image data of the
colors C, M, Y, Mk sent from the binary synthesizer 109 is applied to the
synchronous delay memory 115, where the delay between heads is corrected.
Thereafter, the binary image data of the colors C, M, Y, Mk is supplied
also to the image judging unit 123 at the same time that the corrected
data is printed and recorded by the recording heads 117 through 120. The
image judging unit 123 performs a real-time comparison of the supplied
binary image data and specific image data registered in advance. In a case
where there is a high degree of similarity with image data corresponding
to a specific original, as will be described below, the image judging unit
123 sends a decision signal to the controller 121 to suspend the printing
operation. At this time the controller 121 naturally notifies the
controllers 102, 111 of this event.
In the case of a digital full-color copier of the kind illustrated in this
embodiment, the arrangement is such that the binary image data is capable
of being printed out directly via a host computer and through the
intermediary of the I/F controller 112 and buffer memory 110 . Therefore,
in order to prevent the printing of specific image data through this path,
the image judging unit 123 must be adapted to make this decision from the
binary image data which prevails immediately prior to printing.
FIG. 8 is a block diagram showing the construction of the image judging
unit according to the first embodiment. Numeral 801 denotes a shift
register for converting the pixels signals of the serially delivered
colors C, M, Y, Bk into parallel data . The C, M, Y, Bk serial binary
image data is converted into parallel signals by a timing controller, not
shown.
Numeral 802 denotes a binary/multivalue converter circuit for converting
the binary image data, which has been subjected to the parallel conversion
by the shift register 108, into multivalued image data of five bits per
color. A bit width of four bits is adopted for the following reasons:
Specifically, the bit width is set while requiring that the processing
load on the circuitry following the converter circuit be alleviated and
that a specific original be detectable with a sufficient degree of
certainty. In addition, the image data subjected to the
binary-to-multivalue conversion is so converted by being thinned out in
such a manner that one pixel is multivalue-converted every four pixels.
This also is done for the reason mentioned above.
Numeral 803 designates color-matching look-up table (hereinafter referred
to as a "color-matching LUT") constituted by a ROM which performs the
matching of colors, which are the image characteristics of specific
original of a plurality of types. Numerals 804-1, 804-2, 804-8 denote
color judging circuits each constituted by the same software. Each color
judging circuit includes an integrator 805, a comparator 806 and a
register 807 and determines whether a specific original is present in the
image data. Numeral 808 designates an OR gate. In a case where one or more
of the color judging circuits 804-1, 804-2, ..., 804-8 judges that the
specific original is present in the image data, the OR gate 808 delivers
the output "1" of this judging circuit as a decision signal H.
The details of the binary/multivalue converter circuit 802 will now be
described.
FIGS. 9 through 11 are diagrams for describing the processing performed by
the binary/multivalue converter 802 according to the first embodiment. As
shown in FIG. 9, area processing is applied to the inputted binary image
data. In this embodiment, a 5.times.5 matrix of the kind illustrated in
FIG. 9 is used to determine the total sum of each of the cells in which
the image data is present, thereby obtaining the density level of a pixel
of interest shown at 901 in FIG. 9. At this time a weighting coefficient
is set for each cell. The value which has given by multiplication using
this weighting coefficient is the data of each cell.
As shown in FIG. 10, in which xi, yj represent the weighting coefficients
of the matrix, a density level e of a pixel of interest is determined by
the following equation:
##EQU1##
where a represents the image data and is 1 or 0, since the image is a
binary image.
The weighting coefficients of this embodiment are illustrated in FIG. 11.
In this case, the density level is a decimal number (61) when the density
is maximum. In terms of a binary number, all densities can be expressed by
a data width of five bits.
FIG. 12 is a diagram for describing a method of thinning out image data and
subjecting the image data to a multivalued conversion according to the
first embodiment. In FIG. 12, a pixel of interest 1201 is subjected to a
multivalue conversion, after which the image data to be subjected to this
conversion next is multivalue-converted using image data obtained by
jumping four pixels ahead as the pixel of interest.
The foregoing processing executed by the binary/multivalue converter 802
possesses independent circuitry for each of the colors C, M, Y and Bk. The
image data for each of the colors C, M, Y and Bk thus converted from a
binary value to a multivalue enters the color-matching LUT 803 of FIG. 8.
The color-matching LUT 803 investigates color distribution with regard to
specific originals of eight types in advance and holds the results of
judgment, these results indicating whether the color of a pertinent pixel
coincides with a color of the specific originals.
More specifically, the color-matching LUT 803 has address lines of 20 bits
to which the pixel data of each of the colors C, M, Y, Bk
multivalue-converted by the converter 802 enters five bits at a time. The
data-output lines of the color-matching LUT 803 are of eight bits, each
single bit corresponding to one type of specific original. A total of
eight types of specific originals are judged.
FIG. 13 is a block diagram illustrating the construction of the integrator
805 according to the first embodiment. In FIG. 13, numerals 1301, 1305
denote flip-flops which hold data at the timing of the leading edge of a
clock signal CALK. Numeral 1302 denotes a multiplier to which two
eight-bit signals (A, B) are inputted. The multiplier 1302 multiplies
these signals together and outputs an eight-bit signal
##EQU2##
as the result. Numeral. 1303 denotes a multiplier to which a one-bit input
signal (A) and an eight-bit input signal (B) are applied . The multiplier
1303 multiplies these signals together and outputs an eight-bit signal
(A.times.B) as the result . Numeral 1304 denotes an adder to which two
eight-bit signals (A, B) are inputted. The multiplier 1304 adds these
signals together and outputs an eight-bit signal (A+B) as the result.
Accordingly, in the integrator 805 of this embodiment, an eight-bit output
signal Yi is expressed by the following equation when a binary input
signal x.sub.1 is applied:
Yi=(.alpha./255)yi-1.beta..multidot.x.sub.i-1 (2)
where .alpha. and .beta. represent constants that have been preset. The
various characteristics of the integrator 805 are decided by the sizes of
these values.
A case in which .alpha.=247, .beta.=8 hold will be described as one
example.
FIGS. 14 and 15 are diagrams showing an example of the input/output of the
integrator 805 according to the first embodiment. An output Yi of the kind
shown in FIG. 15 is outputted in response to an input x.sub.i-1 of the
kind shown in FIG. 14.
An input which is "1" despite the fact that almost all values peripheral
thereto are "0", as in the manner of points 14 | | |
